Data printers generally use paper already provided with transversal perforations for the separation of adjacent sheets and furthermore use paper having lateral longitudinal holes which allow it to be dragged by means of paper-dragging rollers provided with small teeth which engage in said holes. The paper, therefore, requires treatment upstream from printing consisting in the unrolling of virgin paper and the forming of lateral holes and transversal perforations, the perforations being produced at a fixed interval such as 12 inches. The paper is then furnished in bobbins or in packages of folded "accordion" sheets.
The presence of the lateral dragging holes normally facilitates the control of the paper during the printing step which can be carried out by means of paper-dragging rollers. The transversal perforations are, on the other hand, normally accompanied by a preceding notch which allows a sensor to inform the printer of the exact position of said perforations in order to allow the printing heads to initiate printing in correspondence to the beginning of each sheet of paper delimited by two consecutive perforations.
The need for printers, especially when of large dimensions, which operate with a continuous strip of paper that has not been pre-processed, and, instead, comes directly from the paper mill in the form of a bobbin, is strongly felt. Such paper obviously lacks lateral dragging holes and transversal perforations. Thus savings are obtained both by the fact that, by not having lateral borders which comprise the dragging holes, the strip is narrower, and thus less paper can be used, and by the fact that, by not having to be pre-processed, the paper can be obtained directly from the mill at a lower price. These two savings are advantageous to large printer users, such as banks, utilities companies, firms, etc. with large numbers of clients to whom it is necessary to communicate information such as invoices, financial statements, bulletins, etc.. The quantity of paper in circulation is enormous, and printers able to satisfy volumes of this nature operate at a considerable velocity, for example 50-100 cm/sec and faster.
A type of data printer which operates using paper not provided with lateral dragging holes and which produces, at the output, by means of shears, single sheets obtained from the strip of paper printed back and front is well-known. The use of the shears makes transversal perforations unnecessary, whereas the absence of the dragging holes is compensated for by processing the paper taut. The control of the beginning position of each printed sheet occurs in correspondence to the printing heads which send corresponding signals to a central processing unit which also commands the shears at the output. Errors in the calculation of the beginning position of each sheet can occur, however, due to sliding of the paper with respect to the dragging rollers or stretching of the paper itself as a result of the tension. Said errors, however, can be reduced to a negligible amount, bringing the printer to function in constant operative conditions.
In many cases, for the control of the quality and accuracy of the printed data, it is necessary that the paper exiting the printer still be in a continuous strip, and produced in folded "accordion", packages. In such cases, it is necessary for the paper, at the beginning of printing, to already have the transversal perforations suitable to allow the tearing apart from one another of adjacent sheets of paper in a later step.
This characteristic, however, implies certain difficulties which currently cannot be overcome in the case that one wishes to carry out printing starting with a virgin strip of paper. Consequently, in these cases, one must use pre-processed paper already comprising lateral dragging holes and transversal perforations.
The object of the present invention is to provide an apparatus for the transversal perforation of paper to insert in printers fed by a continuous strip of paper without lateral dragging holes, in order to allow for the above-mentioned savings.
A further object of the present invention is to provide a method for the transversal perforation, within the printer, of a strip of paper or similar material without lateral dragging holes, in synchronism with the beginning of each printed sheet.
These objects are accomplished by the transversal perforating apparatus according to a method for transversal perforation of a strip of paper within a printer.